import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution8 {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @return int整型一维数组
     */
    public int[] inorderTraversal (TreeNode root) {
        // write code here
        ArrayList<Integer> list = new ArrayList<>();
        inorder(list,root);
        int[] ret = new int[list.size()];
        for(int i = 0;i<list.size();i++) {
            ret[i] = list.get(i);
        }
        return ret;
    }
    private void inorder(ArrayList<Integer> list,TreeNode root) {
        if(root == null) {
            return;
        }
        inorder(list,root.left);
        list.add(root.val);
        inorder(list,root.right);
    }
}